Spam Crusher for Outlook

From American Systems:

Spam Crusher for Outlook integrates right into Microsoft Outlook blocking spam.
As your email arrives Spam Crusher scans the email. If it is spam it is automatically sent to the Junk folder within Outlook.
Spam Crusher is designed to filter unwanted email, while allowing the email you want to receive.
Spam Crusher works in several ways. First, it lets you add the email addresses of those people who are your "friends." The people you want to receive email from. Friends can be added one at a time, or you can import the address book from your email client right into the program.
Spam Crusher will not filter any email from someone on your 'friends' list. Their email will always get through.
Secondly, Spam Crusher blocks out offensive email using a filter list that's made up of thousands of entries. These filters contain domain names and email addresses of known spammers.
The filters also contain offensive words and phrases. And, this list is constantly updated by us.